1. Field of the Invention
The present invention relates to a power converter controller, and more particularly relates to an adaptive power converter controller.
2. Description of Related Art
The technology of constant-voltage to constant-current transferring control is usually applied to Lithium battery chargers and current-limiting constant-voltage regulators. As to Lithium battery chargers, the charging process begins at constant-current mode to fast charging the battery. Then, as the voltage level of the battery reaches a predetermined limitation, the lithium battery chargers would be transformed into constant-voltage mode to clamp the voltage level of the battery to protect the battery. As to current-limiting constant-voltage regulators, the operation begins at constant-voltage mode to restrict the voltage level of output voltage. Then, as the output current reaches a predetermined limitation, the current-limiting constant-voltage regulator would be transformed into constant-current mode to clamp the output current so as to achieve the object of current-limiting protection.
FIG. 1 is a schematic view of a prior art constant-voltage to constant-current transferring controller 10. As shown, the constant-voltage to constant-current transferring controller 10 is electrically coupled to a power converter circuit 11, which is utilized for providing electrical power to a load 12. The constant-voltage to constant-current transferring controller 10 has a voltage sensing circuit 13, a current sensing circuit 14, a DC voltage level converting circuit 151, and an error amplifier 152. The voltage sensing circuit 13 detects the voltage level provided to the load 12 to output a voltage sensing signal VOS accordingly. The current sensing circuit 14 detects the current on the load 12 to output a current sensing signal VCS accordingly. The DC voltage level converting circuit 151 receives the current sensing signal VCS and adjusts the voltage level of the current sensing signal VCS according to a first reference voltage signal VR1 so as to output an adjusted current sensing signal VC1. The error amplifier 152 receives the voltage sensing signal VOS, the adjusted current sensing signal VC1, and a second reference voltage signal VR2 to output a feedback voltage signal VFB.
As the voltage level of the voltage sensing signal VOS over that of the adjusted current sensing signal VC1, the error amplifier 152 generates the feedback voltage signal VFB according to the voltage sensing signal VOS and the second reference voltage signal VR2. That is, the error amplifier 152 adopts voltage feedback control and the constant-voltage to constant-current transferring controller 10 is in constant-voltage mode. As the voltage level of the voltage sensing signal VOS under that of the adjusted current sensing signal VC1, the error amplifier 152 generates the feedback voltage signal VFB according to the adjusted current sensing signal VC1 and the second reference voltage signal VR2. That is, the error amplifier 152 adopts current feedback control and the constant-voltage to constant-current transferring controller 10 is in constant-current mode. Thereby, the object of constant-voltage to constant-current transferring control is achieved.
FIG. 2 is a diagram showing the relationship between output voltage and output current of the power converter circuit 11 by using the constant-voltage to constant-current transferring controller 10 in FIG. 1. As shown, in constant-voltage mode, as the output current close to the predetermined current limit under constant-current mode, the efficiency of constant-voltage feedback control under constant-voltage mode is disturbed by the operation of constant-current feedback control, which results in a reduction of output voltage level and an increasing of feedback error. Therefore, the characteristic of constant-voltage output of the constant-voltage to constant-current transferring controller 10 is influenced.